1. Field of the Invention
A traction control method for dynamically maintaining safe driving traction between a tire and a driving surface in a decelerating motor vehicle, and more particularly toward a traction control method as implemented through a modulated braking device.
2. Related Art
When slowing a motor vehicle, it is important to maintain adequate traction between the tires and the road surface. Vehicle deceleration can be accomplished by way of traditional braking techniques, for example, disc and or brake systems implemented at the vehicle tires, by shaft gearbox and/or drive train braking systems, by regenerative braking systems such as those used to generate electricity or compress air, or by other means.
Traditional braking systems implemented at the vehicle tire have been made more effective by the so-called antilock braking techniques, wherein tire speeds are monitored, and braking devices modulated independently of one another so as to prevent the dangerous loss of tire traction. The prior art has shown that stability reserve calculations can be made while an automobile tire is in motion to determine whether brake pressure should be increased or decreased in an antilock braking scenario. One example of calculating a stability reserve may be found in U.S. Pat. No. 5,070,459 to Van Zanten et al., issued Dec. 3, 1991, the entire disclosure of which is hereby incorporated by reference.
Prior art techniques for calculating the stability reserve have relied on a sequence of events that include the steps of applying brake pressure followed by a pressure release and then an evaluation of the net effect caused by the transitory pressure impulse. When it is time to repeat the sequence, the system resets itself using the new tire stability calculation as a baseline. This series of events is repeated over and over again in rapid succession until the demand abates.
This stability reserve calculation methodology is a rather slow process as the sequence of events (calculate reserve—apply impulse—recalculate reserve—set new baseline) must be repeated throughout each correction cycle. In an emergency stop situation, every millisecond is precious.
There is therefore a need and desire to improve the performance of antilock brake systems to operate faster and with better response times. Furthermore, there is a desire to extend the application of antilock braking techniques to non-traditional braking systems, including regenerative braking systems, with similar traction control benefits.